Herschel Casts New Light on Stellar Formation

The European Space Agency's (ESA) Herschel Space Observatory is the largest telescope ever flown to space, and arguably the most advanced of its class. It surveys the sky in infrared wavelengths, with the express purpose of gaining more data on how the Universe appeared, and how the first stars began forming. It is also very efficient at piercing the massive clouds of cosmic dust and hydrogen gas, which envelop areas that contain stellar nurseries, or nebula. Recent images sent back by Herschel paint one such structure, in the midst of giving birth to young massive stars.

These objects are generally elusive before they ignite, because they form inside very large and very thick cocoons. Other infrared telescopes do not have the necessary observational power to pierce through them, but Herschel – with its three instruments, PACS, SPIRE and HIFI – is perfectly able to collect the most detailed images of these regions ever produced. In addition to the stars themselves, the machine is also shinning new light on previously-unseen details, which were simply too small for other, less-sensitive observatories to detect.

The new image set captures thousands of galaxies and myriads of stars, but also include photographs of exquisite details in various regions. One such region is an area of intense stellar formation known as RCW 120, which features a protostar in the process of collapsing in on itself, and producing a massive new star. These fireballs are several tens of times more massive than the Sun, and several times over as large. The process through which they form is, however, still shrouded in mystery, due to the fact that they cloak themselves using their thick cocoons.

Astronomers say that the recently-identified baby stars will most likely become one of the largest and brightest in the Milky Way within the next few hundreds of thousands of years. According to Herschel readings, the fireball is already 8 to 10 times the mass of the Sun, but it has more than 1000 solar masses-worth of gas and dust in its immediate vicinity. From this mass, it can continuously feed and fuel its burning process. “This star can only grow bigger. To catch one during formation presents a golden opportunity to solve a long-standing paradox in astronomy. According to our current understanding, you should not be able to form stars larger than eight solar masses,” says Laboratoire d’Astrophysique de Marseille expert Annie Zavagno.